Embryonic Stem Cells as a Model for the Physiological Analysis of the Cardiovascular System

Embryonic stem (ES) cells have the potential to proliferate infinitely in vitro in an undifferentiated and pluripotent state, thereby maintaining a relatively normal and stable karyotype even with continual passaging. Remarkably, in vivo, ES cells can be reincorporated into normal embryonic development by transfer into a host blastocyst or aggregation with blastomere stage embryos. They can contribute to all tissues in the resulting chimeras including gametes. When cultivated in vitro, ES cells differentiate under appropriate cell culture conditions, i.e., in the absence of leukemia inhibitory factor (LIF) into cell types of all three germ layers: endoderm, ectoderm and mesoderm (1 ). However, these differentiation processes occur only when ES cells are cultivated in suspension culture in which they grow to multicellular spheroidal tissues, termed embryoid bodies (EBs).